The features of the energetics and electronic properties of carbon nanotubes, containing a pentagon-heptagon pair (5/7) topological defect in the hexagonal network of the zig-zag configuration, were investigated using the extended Su-Schriffer-Heeger model based upon the tight binding approximation in real space. The calculations showed that this pentagon-heptagon pair defect in the nanotube structures was responsible not only for a change in nanotube diameter, but also governed the electronic behavior around the Fermi level. The densities of states of the (9,0)-(8,0) and (8,0)-(7,0) systems were calculated. For the (9,0)-(8,0) system, a narrow gap existed in the vicinity of the Fermi energy. For the (8,0)-(7,0) system, a little peak in the density of states occurred at the Fermi energy. These could be attributed to the addition of a pair of pentagon-heptagon defects to the interface between two isolated carbon nanotubes.

Electronic Properties of Carbon Nanotubes with a Pentagon-Heptagon Pair Defect. H.F.Hu, Y.B.Li, W.Y.Zhou, D.S.Tang: Chinese Physics, 2001, 10[6], 531-6